 An electron passes perpendicularly through a magnetic field at a velocity of 2.0x10 7 m/s. The strength of the magnetic field is 0.25 T. What is the magnitude of the force acting on the electron. 8.0x N

 Clear everything off of your desk except writing utensils and erasers.  Make sure all electronic devices (cell phones, iPods, smart watches, etc.) are powered off and in your backpack (not your pocket).  If you appear to be talking, looking at another student’s quiz, allowing another student to look at your quiz, or using any unauthorized aide, you will receive a zero.  If any electronic device is seen or heard, it goes to the office, and you will receive a zero.

Chapter 25

 Current  Magnetic field  Changing magnetic field  Current  Electromagnetic induction is the creation of current by a changing/moving magnetic field.  The wire must cross magnetic field lines (not parallel to magnetic field).

 An electric generator converts mechanical energy into electrical energy  Works similar to a Galvanometer or electric motor in reverse  A wire is looped inside a magnetic field.  When the loop is rotated, an EMF generates a current

 AC/DC = Alternating Current / Direct Current  Direct current goes in one direction ◦ All of the problems we have done so far are for a constant direct current  Electric generators produce alternating current  Alternating current switches direction multiple times per second  AC in United States has a frequency of 60 Hz

 Electricity can be transmitted at very high voltage using AC  This allows less heat loss (more of the electricity makes it to your house)  This is more economical (saves money)  The voltage can be lowered to safer values using transformers.

 A wire is moving perpendicular to a 0.10 T magnetic field with a speed of 1.5 m/s. If the wire is 30.0 cm long, how much electromotive force is generated? V

 A transformer contains two coils wrapped around the same iron core  Passing an alternating current through one coil will induce a current in the other coil  If the number of loops are different, then the voltage and current will be different

 A step-down transformer has 7500 turns on its primary coil and 125 turns on its secondary coil. The voltage across the primary circuit is 7.2 kV. The current in the secondary circuit is 36 A. a) What voltage is being applied across the secondary circuit? b) What is the current in the primary circuit? a)120 V b)0.60 A

 A step-up transformer has exactly 300 turns on its primary coil and exactly 90,000 turns on its secondary coil. The EMF of the generator to which the primary circuit is attached is 60.0 V. The current in the secondary circuit is 0.50 A. a) What is the EMF of the secondary circuit? b) What is the current in the primary circuit? a)18,000 V b)150 A

 Can amplify an electric signal.  Can be used as a switch.  Used in almost all modern electronic devices.

 HIY HIY

 Overly simplified diagram:

 Read Chapter 25  Page #31, 32, 42, 60, 76  Electricity and Magnetism Review  Expect a test on Chapters on May 4/5

 What electromotive force is produced when a 35 cm long wire is moving through a T magnetic field at 0.81 m/s?

 QUIETLY read through your lab packet.  For each trial, you will make a prediction.  AFTER your prediction, you will perform the test, and then write down your observation.